Abstract:

A lens barrel capable of achieving a smooth zoom operation and reducing a
driving load at the time of barrel retraction. The lens barrel includes a
rectilinear guide cylinder rectilinearly moving in an optical axis
direction, and a movable cam cylinder moving in the optical axis
direction while rotating relative to the guide cylinder. The guide
cylinder is formed at its inner peripheral surface with a cam groove and
a rectilinear guide groove that divides the cam groove at a boundary
between a retracted region and a photographing region, and is formed with
a penetration cam groove extending from the inner peripheral surface to
an outer peripheral surface of the guide cylinder. The movable cam
cylinder moves in the photographing region while the first pin engages
the cam groove, and moves in the retracted region while the second pin
engages the penetration cam groove.

Claims:

1. A lens barrel comprising:a rectilinear guide cylinder configured to
rectilinearly move in an optical axis direction, said rectilinear guide
cylinder having at least one cam groove formed on an inner peripheral
surface thereof, at least one penetration cam groove extending from the
inner peripheral surface to an outer peripheral surface thereof, and at
least one rectilinear guide groove extending in the optical axis
direction and dividing the cam groove at a boundary between a retracted
region and a photographing region; anda movable cam cylinder configured
to move in the optical axis direction while rotating relative to said
rectilinear guide cylinder, said movable cam cylinder having at least one
first pin that engages the cam groove and at least one second pin that
engages the penetration cam groove,wherein said movable cam cylinder
moves in the photographing region while the first pin engages the cam
groove, and moves in the retracted region while the second pin engages
the penetration cam groove.

2. The lens barrel according to claim 1, wherein a chamfer is formed at a
portion of the cam groove where the cam groove is divided by the
rectilinear guide groove.

3. The lens barrel according to claim 1, wherein the first pin is a taper
pin, and the second pin is a circular cylindrical pin.

4. An image pickup apparatus comprising the lens barrel as set forth in
claim 1.

Description:

BACKGROUND OF THE INVENTION

[0001]1. Field of the Invention

[0002]The present invention relates to a lens barrel capable of zoom
operation, and relates to an image pickup apparatus such as a digital
camera having the lens barrel.

[0003]2. Description of the Related Art

[0004]Some conventional zoom lens barrel includes a fixed cylinder having
an inner peripheral surface thereof formed with cam grooves, a cam
cylinder having cam pins for engagement with the cam grooves of the fixed
cylinder, and a lens retainer having cam pins for engagement with cam
grooves formed on an inner peripheral surface of the cam cylinder. The
cam cylinder moves along an optical axis direction while rotating. With
rotation of the cam cylinder, the lens retainer relatively moves in the
optical axis direction for zooming and retracting operations.

[0005]With recent trend that image pickup apparatuses are made smaller in
thickness and higher in magnification, the zoom lens barrel of the above
construction has rectilinear guide grooves for causing the lens retainer
to rectilinearly move in the optical axis direction. The rectilinear
guide grooves are formed on the inner peripheral surface of the fixed
cylinder so as to extend across and divide the cam grooves formed on the
fixed cylinder.

[0006]However, the rectilinear guide grooves formed in this manner cause a
fear that the cam pins of the lens retainer are disengaged from the cam
grooves of the fixed cylinder at positions where the cam grooves are
divided by the rectilinear guide grooves, or that the cam pins or the cam
grooves are worn.

[0007]Thus, a zoom lens barrel has been proposed in which first and second
cam grooves used in respective ones of a photographing region and a
non-photographing region are formed on the inner peripheral surface of
the fixed cylinder and in which first and second cam pins for engagement
with respective ones of the first and second cam grooves are formed on
the outer peripheral surface of the cam cylinder (Japanese Laid-open
Patent Publication No. 2006-220898).

[0008]This proposal contemplates to smoothly drive the zoom lens barrel by
engaging the second cam pins with the second cam grooves not divided by
the rectilinear guide grooves when the first cam pins are at positions
where the first cam grooves are divided by the rectilinear guide grooves.

[0009]However, this lens barrel causes a fear that the cam pins are caught
in cam groove entrances at the time of switching between the retracted
region and the photographing region so that the zoom operation is
adversely affected. In addition, a relatively large driving load is
applied to the lens barrel at the time of barrel retraction and at the
time of photographing since the cam pins are in engagement with the cam
grooves both in the retracted region and in the photographing region.

SUMMARY OF THE INVENTION

[0010]The present invention provides a lens barrel and an image pickup
apparatus, which are capable of achieving a smooth zoom operation and
reducing a driving load at the time of barrel retraction.

[0011]According to a first aspect of this invention, there is provided a
lens barrel comprising a rectilinear guide cylinder configured to
rectilinearly move in an optical axis direction, the rectilinear guide
cylinder having at least one cam groove formed on an inner peripheral
surface thereof, at least one penetration cam groove extending from the
inner peripheral surface to an outer peripheral surface thereof, and at
least one rectilinear guide groove extending in the optical axis
direction and dividing the cam groove at a boundary between a retracted
region and a photographing region, and a movable cam cylinder configured
to move in the optical axis direction while rotating relative to the
rectilinear guide cylinder, the movable cam cylinder having at least one
first pin that engages the cam groove and at least one second pin that
engages the penetration cam groove, wherein the movable cam cylinder
moves in the photographing region while the first pin engages the cam
groove, and moves in the retracted region while the second pin engages
the penetration cam groove.

[0012]According to a second aspect of this invention, there is provided an
image pickup apparatus which comprises the lens barrel according to the
first aspect of this invention.

[0013]With this invention, it is possible to achieve a smooth zoom
operation of the lens barrel having the rectilinear guide cylinder formed
with at least one guide groove and at least one rectilinear guide groove
extending across and dividing the cam groove and to reduce a driving load
at the time of barrel retraction.

[0014]Further features of the present invention will become apparent from
the following description of an exemplary embodiment with reference to
the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is a section view showing a lens barrel according to one
embodiment of this invention in a retracted state;

[0016]FIG. 2 is a section view showing the lens barrel in a WIDE state;

[0017]FIG. 3 is a section view showing the lens barrel in a TELE state;

[0018]FIG. 4 is an exploded perspective view of the lens barrel;

[0019]FIG. 5 is a perspective view showing an assembly of a CCD holder and
a third group barrel of the lens barrel;

[0020]FIG. 6 is a development view of an inner peripheral surface of a
fixed cam cylinder of the lens barrel;

[0021]FIG. 7 is a development view of an inner peripheral surface of a
first movable cam cylinder of the lens barrel;

[0022]FIG. 8 is a development view of an outer peripheral surface of a
first rectilinear guide cylinder of the lens barrel;

[0023]FIG. 9 is a development view of an inner peripheral surface of the
first rectilinear guide cylinder;

[0024]FIG. 10 is a development view of an inner peripheral surface of a
second movable cam cylinder of the lens barrel;

[0025]FIG. 11 is an exploded perspective view of a first group barrel of
the lens barrel;

[0026]FIG. 12 is an exploded perspective view showing the first movable
cam cylinder and the first rectilinear guide cylinder;

[0027]FIG. 13 is an exploded perspective view showing the second movable
cam cylinder and a second rectilinear guide cylinder of the lens barrel;

[0028]FIGS. 14A and 14C are views each showing a state of engagement
between a drive pin of the second movable cam cylinder and a penetration
cam groove of the first rectilinear guide cylinder;

[0029]FIGS. 14B and 14D are views each showing a state of engagement
between a follower pin and a cam groove of the first rectilinear guide
cylinder; and

[0030]FIG. 15 is an enlarged fragmentary view showing chamfers formed at
the cam groove of the first rectilinear guide cylinder.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0031]The present invention will now be described in detail below with
reference to the drawings showing a preferred embodiment thereof.

[0032]FIGS. 1 to 3 show in section view a lens barrel according to one
embodiment of this invention in a retracted state, in a WIDE state, and
in a TELE state, respectively.

[0033]FIG. 4 shows the lens barrel in exploded perspective view, and FIG.
5 shows in perspective view an assembly of a CCD holder and a third group
barrel of the lens barrel.

[0034]The lens barrel of this embodiment is configured as a zoom lens
barrel adapted to be mounted on an image pickup apparatus such as a
digital camera. The lens barrel includes a first group barrel 201 that
holds a first lens group 101, a second group unit (hereinafter, denoted
by reference numerals 202, 203) including a second group holder 202 that
holds a second lens group 102 and a second group base 203 that has an
aperture and a shutter, and a third group barrel 204 that holds a third
lens group 103.

[0035]The first group barrel 201 and the second group unit 202, 203 are a
zooming system lens group. The second group unit includes an anti-shake
mechanism for correcting hand shake at the time of photographing or the
like. The third group barrel 204 is a focus lens group for focusing on
the object.

[0037]The CCD holder 206 is fastened to the fixed cam cylinder 205. A CCD
sensor 104 is mounted to the CCD holder 206 via a CCD plate 11. An
optical filter 14 is disposed on the object side of the CCD sensor 104
and interposed between a CCD mask 12 and a CCD rubber 13.

[0038]As shown in FIG. 5, photo interrupters 36, 37 for detecting initial
lens positions at zooming and focusing are attached to the CCD holder
206. A zoom motor 212 is fixed to the CCD holder 206, and a rotational
driving force of the motor 212 is conveyed to a gear 211 via a gear train
213. Pulses generated by the zoom motor 212 are counted by photo
interrupters 38, 39. The details of the photo interrupters 36-39 will be
described later.

[0039]The third group barrel 204 is supported by the CCD holder 206 so as
to be movable in the optical axis direction. Specifically, an AF guide
shaft 31 extending parallel to the photographing optical axis and
slidably fitted to a guide hole 204a formed in the third group barrel 204
is press-fitted and fixed to the CCD holder 206. A sub-guide shaft 32 for
rotation restriction is integrally formed with the CCD holder 206.

[0040]The third group barrel 204 is urged by an AF spring 33 toward the
object side in the optical axis direction. On the object side of the
third group barrel 204, there is provided an AF nut (not shown) that
threadedly engages a screw (not shown) of an AF motor 34. With rotation
of the screw of the AF motor 34, the third group barrel 204 is moved to
advance and retreat in unison with the AF nut in the optical axis
direction.

[0041]A light shield plate 204b is integrally formed with the third group
barrel 204 and disposed to be movable to advance to and retreat from a
slit portion of the photo interrupter 37. Springs 35 that urge the second
group unit toward the object side in the optical axis direction at the
time of barrel retraction are disposed at three places on the CCD holder
206.

[0042]FIG. 6 shows an inner peripheral surface of the fixed cam cylinder
205 in development view.

[0043]As shown in FIG. 6, cam grooves 205a are formed at circumferentially
equal intervals at three places on the inner peripheral surface of the
fixed cam cylinder 205, and rectilinear guide grooves 205b extending
parallel to the optical axis are formed at three places on the cylinder
205.

[0044]The first movable cam cylinder 207 is disposed on the inner
periphery side of the fixed cam cylinder 205, as shown in FIGS. 1 to 4.
Three follower pins 207a (FIG. 12) that engage the cam grooves 205a of
the fixed cam cylinder 205 are formed on the outer peripheral surface of
the first movable cam cylinder 207 integrally therewith.

[0045]A gear portion 207g having gear tooth extending parallel to the
photographing optical axis is formed on the outer peripheral surface of
the first movable cam cylinder 207. When rotation of the gear 211 is
conveyed to the gear portion 207g, the first movable cam cylinder 207
moves in the optical axis direction while being rotated by cam engagement
between the follower pins 207a and the cam grooves 205a of the fixed cam
cylinder 205.

[0046]FIG. 7 shows an inner peripheral surface of the first movable cam
cylinder 207 in development view.

[0047]As shown in FIG. 7, second group cam grooves 207b along which the
second group unit 202, 203 is moved in the optical axis direction are
formed at circumferentially equal intervals at three places on the inner
peripheral surface of the first movable cam cylinder 207.

[0048]A rear end portion (on the side remote from the object side) of a
groove portion 207f of each second group cam groove 207b is omitted,
whereby the entire length of the lens barrel at the time of barrel
retraction can be shortened. A description of how the second group unit
is held by the first movable cam cylinder 207 at the time of barrel
retraction will be given later.

[0049]Cam grooves 207c extending in the circumference direction are formed
at circumferentially equal intervals at three places on a front-end-side
inner peripheral surface of the first movable cam cylinder 207.

[0050]Dual groove portions 207d1, 207d2; 207d3, 207d4; and 207d5, 207d6
extending in the circumference direction are formed at circumferentially
equal intervals on a rear-end-side inner peripheral surface of the first
movable cam cylinder 207.

[0051]A distance between the groove portions 207d1, 207d2 in the optical
axis direction is set to be wider than a distance between the groove
portions 207d3, 207d4 in the optical axis direction. The distance between
the groove portions 207d3, 207d4 is set to be wider than a distance
between the groove portions 207d5, 207d6 in the optical axis direction.

[0052]On the inner periphery side of the first movable cam cylinder 207,
the first rectilinear guide cylinder 208 is disposed to be slidable
relative to the cam cylinder 207 in the rotating direction (FIG. 1). In
FIG. 7, reference numeral 207e denotes rectilinear driving grooves with
which drive pins 209b of the second movable cam cylinder 209 are engaged,
and reference numerals 209b1 to 209b3 denote positions of the drive pins
209b in the retracted state, in the WIDE state, and in the TELE state,
respectively.

[0053]FIG. 8 shows an outer peripheral surface of the first rectilinear
guide cylinder 208 in development view.

[0054]As shown in FIG. 8, penetration cam grooves 208e and first
rectilinear guide grooves 208f are respectively formed at
circumferentially equal intervals at three places on the first
rectilinear guide cylinder 208. Taper pins 208a engaging the cam grooves
207c of the first movable cam cylinder 207 are formed at
circumferentially equal intervals at three places on a front end portion
of the first rectilinear guide cylinder 208.

[0055]The taper pins 208a of the first rectilinear guide cylinder 208 are
engaged with the cam grooves 207c of the first movable cam cylinder 207,
whereby play between the cam cylinder 207 and the guide cylinder 208 in
the optical axis direction and in the radial direction can be eliminated
and impact resistance can be improved.

[0056]Rectangular pins 208b1 to 208b6 corresponding to the groove portion
207d1 to 207d6 of the first movable cam cylinder 207 are projectingly
provided on a rear end portion of the first rectilinear guide cylinder
208.

[0057]In FIG. 8, symbol X denotes regions of the guide cylinder 208 each
surrounded by corresponding ones of the penetration cam grooves 208e and
the first rectilinear guide grooves 208f, and symbol Y denotes regions of
the guide cylinder 208 each located on the front end side (object side)
in the optical axis direction with respect to the corresponding
penetration cam groove 208e. Since the penetration cam grooves 208e and
the first rectilinear guide grooves 208f are formed around the regions X,
the regions X supported at Z1 and Z2 portions are lower in impact
resistance than the regions Y.

[0058]The taper pins 208a are formed in the regions Y, and the rectangular
pins 208b1-208b6 are formed in the regions X. The rectangular pins 208b2,
208b4, and 208b6 are disposed at the same position in the optical axis
direction as one another. The rectangular pins 208b1, 208b3, and 208b5
are disposed at different positions in the optical axis direction from
one another.

[0059]The groove portions 207d1-207d6 are each formed to have a width
wider than that of a corresponding one of the rectangular pins
208b1-208b6. Accordingly, there is a gap in each of convex-concave
fitting portions between the rectangular pins 208b1-208b6 and the groove
portions 207d1-207d6.

[0060]When the first movable cam cylinder 207 moves in the optical axis
direction while rotating, the rectangular pins 208b1-208b6 do not closely
engage the groove portions 207d1-207d6. The rectangular pins 208b1-208b6,
when applied with a falling impact or the like, therefore function as
static-pressure receiving portions that ensure the impact resistance,
without hindering a zoom operation of the lens barrel.

[0061]Rectilinear guide keys 208h are formed at circumferentially equal
intervals at three places on the outer periphery of the first rectilinear
guide cylinder 208. These rectilinear guide keys 208h are cam-engaged
with the rectilinear guide grooves 205b of the fixed cam cylinder 205,
whereby rotation of the first rectilinear guide cylinder 208 is
restricted when the guide cylinder 208 moves in the optical axis
direction (FIGS. 5, 8, and 12).

[0062]Specifically, the first movable cam cylinder 207 is coupled to the
first rectilinear guide cylinder 208, with reduced play in the optical
axis direction and in the radial direction. When the cam cylinder 207
moves in the optical axis direction while being rotated by a driving
force output from the gear train 213, the guide cylinder 208 is
bayonet-connected to the cam cylinder 207 and rectilinearly moves in the
optical axis direction.

[0063]FIG. 9 shows an inner peripheral surface of the first rectilinear
guide cylinder 208 in development view.

[0064]Cam grooves (both halves of each cam groove are denoted by 208c,
208d), which are the same in shape as but different in circumferential
phase from the penetration cam grooves 208e, and second rectilinear guide
grooves 208g extending parallel to the optical axis are formed at
circumferentially equal intervals at three places on the inner peripheral
surface of the first rectilinear guide cylinder 208. In the following,
the cam groove halves 208c, 208d will be sometimes referred to as the cam
grooves 208c, 208d.

[0065]Each cam groove is divided into two (i.e., cam grooves 208c, 208d)
by a corresponding one of the first rectilinear guide grooves 208f. As
shown in FIG. 15, chamfers 208c1, 208d1 are formed at the divided
portions of the cam grooves. The first rectilinear guide grooves 208f
restrict the second group unit 202, 203 from rotating when the second
group unit moves in the optical axis direction.

[0066]As shown in FIG. 4, the second group base 203 of the second group
unit has three follower pins 203a engaging the second group cam grooves
207b of the first movable cam cylinder 207. Each follower pin 203a has a
root 203b that engages a corresponding one of the first rectilinear guide
grooves 208f of the first rectilinear guide cylinder 208.

[0067]When the first movable cam cylinder 207 moves in the optical axis
direction while rotating, the second group unit 202, 203 moves in the
optical axis direction to follow the cam grooves 207b of the cam cylinder
207.

[0068]As shown in FIGS. 1 and 4, the second movable cam cylinder 209 and
the second rectilinear guide cylinder 210 are disposed on the inner
periphery side of the first rectilinear guide cylinder 208.

[0069]As shown in FIG. 13, follower pins 209a engaging the cam grooves
208c, 208d of the first rectilinear guide cylinder 208 and drive pins
209b extending through the penetration cam grooves 208e of the first
rectilinear guide cylinder 208 are provided on the outer peripheral
surface of the second movable cam cylinder 209. Each follower pin 209a is
a taper pin as with follower pins of other cylinders, whereas each drive
pin 209b is a circular cylindrical pin. Each follower pin 209a is an
example of a first pin of this invention, and each drive pin 209b is an
example of a second pin of this invention.

[0070]The drive pins 209b engage the rectilinear driving grooves 207e of
the first movable cam cylinder 207. With rotation of the cam cylinder
207, the second movable cam cylinder 209 rotates in unison with the cam
cylinder 207 and moves in the optical axis direction by engagement
between the follower pins 209a of the cam cylinder 209 and the cam
grooves 208c, 208d of the first rectilinear guide cylinder 208.

[0071]As described above, the cam grooves 208c of the first rectilinear
guide cylinder 208 are divided from the cam grooves 208d by the guide
grooves 208f. It is the cam grooves 208d in the photographing region that
are engaged with the follower pins 209a of the second movable cam
cylinder 209. The cam grooves 208c in the retracted region are each
formed to be wider than the corresponding follower pin 209a and are not
closely engaged with the follower pins 209a.

[0072]The penetration cam grooves 208e formed in the first rectilinear
guide cylinder 208 each have a width that gradually increases at a
position short of a location where the retracted region shifts to the
photographing region (WIDE position), so that the cam grooves 208e
closely engage the drive pins 209b of the second movable cam cylinder 209
only in the retracted region. In the photographing region where the width
of the cam grooves 208e gradually increases to be larger than that of the
drive pins 209b, the cam grooves 208e do not closely engage the drive
pins 209b.

[0073]Thus, in the retracted region, the drive pins 209b of the second
movable cam cylinder 209 are in engagement with the penetration cam
grooves 208e of the first rectilinear guide cylinder 208. In the
photographing region, the follower pins 209a of the cam cylinder 209 are
in engagement with the cam grooves 208d of the guide cylinder 208. In
FIG. 9, symbols TELE, WIDE, and SINK denote TELE positions, WIDE
positions, and retracted positions of the pins 209a, 209b.

[0074]FIG. 10 shows an inner peripheral surface of the second movable cam
cylinder 209 in development view.

[0075]Cam grooves 209c, 209d along which the first group barrel 201 is
moved in the optical axis direction are formed at circumferentially equal
intervals at three places on the inner peripheral surface of the second
movable cam cylinder 209. The cam grooves 209c are disposed to be
separated from the cam grooves 209d in the optical axis direction.

[0076]Inside the second movable cam cylinder 209, there is disposed the
second rectilinear guide cylinder 210 so as to be slidable in the
rotational direction relative to the second movable cam cylinder 209.

[0077]By the sliding contact between the inner peripheral surface of the
second movable cam cylinder 209 and the outer peripheral surface of the
second rectilinear guide cylinder 210, the cam cylinder 209 and the guide
cylinder 210 are relatively rotatable without play in radial direction.

[0078]The second movable cam cylinder 209 is bayonet-coupled at its inner
peripheral surface to the outer peripheral surface of the second
rectilinear guide cylinder 210. When the cam cylinder 209 moves in the
optical axis direction while rotating, the guide cylinder 210 moves in
the optical axis direction in unison with the cam cylinder 209.

[0079]At that time, rectilinear guide keys 210e formed on the outer
periphery of the second rectilinear guide cylinder 210 engage the second
rectilinear guide grooves 208g formed on the inner peripheral surface of
the first rectilinear guide cylinder 208, whereby the second rectilinear
guide cylinder 210 is restricted from rotating when it moves in the
optical axis direction.

[0080]When the second movable cam cylinder 209 starts rotationally moving
with rotational movement of the first movable cam cylinder 207, the
second rectilinear guide cylinder 210 is bayonet-coupled to the cam
cylinder 209 and starts rectilinearly moving in the optical axis
direction.

[0081]Guide grooves 210a that rectilinearly guide a movement of the first
group barrel 201 in the optical axis direction are formed at
circumferentially equal intervals at three places on the outer periphery
of the second rectilinear guide cylinder 210. A light shield plate 210f
(FIG. 13) is formed integrally with the guide cylinder 210 and disposed
to be movable to advance to and retreat from a slit portion of the zoom
photo interrupter 36.

[0082]The light shield plate 210f enters the slit portion of the photo
interrupter 36 at the time of lens barrel retraction and retreats from
the slit portion in the optical axis direction at the time of lens barrel
extension.

[0083]As shown in FIGS. 1 and 4, the first group barrel 201 is disposed on
the inner periphery side of the second movable cam cylinder 209. As shown
in FIG. 11, follower pins 201a, 201b which are the same in
circumferential phase as each other but different in shape and in
position in the optical axis direction from each other are formed at
circumferentially equal intervals at three places on the first group
barrel 201. The follower pins 201a are disposed on the object side with
respect to the follower pins 201b.

[0084]The follower pins 201a are formed integrally with the first group
barrel 201 and engaged with the cam grooves 209c of the second movable
cam cylinder 209. The follower pins 201b each made of, e.g., a metal pin
are press-fitted and fixed to the first group barrel 201, and loosely
engaged with the cam grooves 209d of the cam cylinder 209. The cam
grooves 209d each having a groove width wider than that of the follower
pins 201b do not closely engage the follower pins 201b.

[0085]By the engagement between the follower pins 201a and the cam grooves
209c, play between the first group barrel 201 and the cam cylinder 209 in
the optical axis direction is eliminated. The follower pins 201b function
to enhance the impact resistance, e.g., falling impact resistance.

[0086]On an inner peripheral surface of the first group barrel 201,
engagement portions (not shown) are formed that engage the rectilinear
guide grooves 210a formed on an outer peripheral portion of the guide
cylinder 210. These engagement portions function to guide a movement of
the first group barrel 201 in the optical axis direction.

[0087]When the second movable cam cylinder 209 moves in the optical axis
direction while rotating, the first group barrel 201 rectilinearly moves
in the optical axis direction without rotating.

[0088]Next, with reference to FIG. 11, a lens barrier mechanism attached
to the first group barrel 201 will be described.

[0089]As shown in FIG. 11, the lens barrier mechanism for closing the
photographing opening at non-photographing time to protect the
photographing optical system is provided on a front end portion of the
first group barrel 201.

[0090]The lens barrier mechanism includes barrier blades 22 that protect
the photographing optical system, a barrier drive ring 24 that drives the
barrier blades 22 in either the closing or opening direction, and barrier
springs 23 each coupled at both ends to the corresponding barrier blade
22 and the barrier drive ring 24. On the object side of the barrier
blades 22, there is provided a barrier cover 21 which is formed with the
photographing opening and which covers the barrier blades 22.

[0091]The barrier drive ring 24 is provided with an extension piece 24a
extending toward the image surface. When the extension piece 24a is in
contact with a reception portion 210b of the second rectilinear guide
cylinder 210 (see FIG. 13), the barrier springs 23 urge the barrier
blades 22 in the closing direction so that the photographing opening of
the barrier cover 21 is closed by the barrier blades 22.

[0092]When the extension piece 24a is disengaged from the reception
portion 210b of the guide cylinder 210, the barrier drive ring 24 is
rotated by the urging forces of the barrier springs 23, and blade contact
portions 24b of the barrier drive ring 24 press and urge the barrier
blades 22 in the opening direction, whereby the photographing opening of
the barrier cover 21 is opened.

[0093]Next, a description will be given of extension and storage
operations of the lens barrel.

[0094]When the lens barrel is in the storage state (retracted state) shown
in FIG. 1, the follower pins 201a of the first group barrel 201 engage
the cam grooves 209c of the second movable cam cylinder 209.

[0095]The second group unit 202, 203 is urged by the springs 35 toward the
object side in the optical axis direction, and held in a state pressed
against object-side surfaces of the cam grooves 207f formed in the first
movable cam cylinder 207.

[0096]The photographing opening of the barrier cover 21 of the lens
barrier mechanism attached to the first group barrel 201 is closed by the
barrier blades 22.

[0097]To shift the lens barrel from the storage state to the photographing
state, the driving force of the zoom motor 212 is conveyed via the gear
train 213 to the gear 211, whereby the first movable cam cylinder 207 is
moved and extended in the optical axis direction while being rotated by
the engagement between the follower pins 207a of the cam cylinder 207 and
the cam grooves 205a of the fixed cam cylinder 205.

[0098]At that time, the first rectilinear guide cylinder 208 is
bayonet-coupled at the taper pins 208a to the cam grooves 207c of the
first movable cam cylinder 207, so that the guide cylinder 208 is
supported without play in the optical axis direction and in the radial
direction, and rectilinearly moves in unison with the cam cylinder 207,
while rotation of the guide cylinder 208 being restricted by the fixed
cam cylinder 205.

[0099]When the first movable cam cylinder 207 is extended in the optical
axis direction, the second group unit 202, 203 rectilinearly moves in the
optical axis direction by the engagement between the follower pins 203a
of the second group base 203 and the cam grooves 207b of the first
movable cam cylinder 207, while being rectilinearly guided by the first
rectilinear guide cylinder 208.

[0100]With the extending operation of the first movable cam cylinder 207,
the second movable cam cylinder 209 is extended in the optical axis
direction and moves in the retracted region, while rotating, by the
engagement between the drive pins 209b of the cam cylinder 209 and the
penetration cam grooves 208e of the first rectilinear guide cylinder 208.

[0101]In FIG. 7, reference numeral 209b1 denotes positions of the drive
pins 209b of the second movable cam cylinder 209 (which is in the
retracted position) in the driving grooves 207e of the first movable cam
cylinder 207. All the three drive pins 209b at the illustrated positions
are in engagement with respective ones of the driving grooves 207e.

[0102]As shown in FIG. 14B, the follower pins 209a of the second movable
cam cylinder 209 in the retracted region are not closely engaged with the
cam grooves 208c of the first rectilinear guide cylinder 208.

[0103]On the other hand, as shown in FIG. 14A, the drive pins 209b are
engaged with the penetration cam grooves 208e in the optical axis
direction, but not restricted in the radial direction. Thus, there is
play in the radial direction between the first rectilinear guide cylinder
208 and the second movable cam cylinder 209. In the retracted region
which is a non-photographing region, some play between the guide cylinder
208 and the cam cylinder 209 does not pose a problem. By allowing radial
play, a load in driving the lens barrel at the time of barrel retraction
can be reduced.

[0104]As shown in FIG. 7, the driving grooves 207e of the first movable
cam cylinder 207 are connected with respective ones of the groove
portions 207d1, 207d3, 207d5 of the cam cylinder 207. When the second
movable cam cylinder 209 is extended from the retracted state, each drive
pin 209b passes through a corresponding one of the connections between
the driving grooves 207e and the groove portions 207d1, 207d3, 207d5.

[0105]Since the groove portions 207d1, 207d3, 207d5 are at different
positions in the optical axis direction, when one of the drive pins 209b
passes through the connection between corresponding ones of the driving
grooves 207e and the groove portions 207d1, 207d3, and 207d5, the other
two drive pins 209b are in stable engagement with the driving grooves
207e at places other than their corresponding connections, and therefore,
the zoom operation is not adversely affected

[0106]In the WIDE state and in the TELE state, the drive pins 209b of the
second movable cam cylinder 209 are at the positions denoted by reference
numerals 209b2 and 209b3 in FIG. 7. In other words, all the three drive
pins 209b in the photographing region are in stable engagement with the
driving grooves 207e, and a smooth zoom operation can be performed.

[0107]Since the cam grooves 208c of the first rectilinear guide cylinder
208 are divided from the cam grooves 208d by the first rectilinear guide
grooves 208f at locations short of the WIDE position, the follower pins
209a are disengaged from the cam grooves 208c when the second movable cam
cylinder 209 moves in the optical axis direction while rotating. When the
cam cylinder 209 further moves in the optical axis direction, the
follower pins 209a enter the cam grooves 208d.

[0108]In the photographing region, the width of the penetration cam
grooves 208e becomes gradually wide, and the drive pins 209b are no
longer closely engaged with the penetration cam grooves 208e as shown in
FIG. 14C. On the other hand, the follower pins 209a closely engage the
cam grooves 208d as shown in FIG. 14D, and the second movable cam
cylinder 209 is held in the photographing region (WIDE position) (FIG.
2).

[0109]As shown in FIG. 15, the chamfers 208d1 are formed at locations
where the cam grooves 208d are divided from the cam grooves 208c, and
therefore, the follower pins 209a can enter the cam grooves 208d without
being caught, so that a smooth zoom operation can be achieved.

[0110]Since each of the follower pins 209a is a taper pin, the follower
pins 209a closely engage the cam grooves 208d in a photographing state,
so that the second movable cam cylinder 209 is held without play relative
to the first rectilinear guide cylinder 208 in the optical axis direction
and in the radial direction.

[0111]The second rectilinear guide cylinder 210 is bayonet-coupled to the
second movable cam cylinder 209 and rotation of the guide cylinder 210 is
restricted by the engagement between the rectilinear guide keys 210e and
the second rectilinear guide grooves 208g formed in the first rectilinear
guide cylinder 208. Accordingly, when the cam cylinder 209 moves in the
optical axis direction while rotating, the guide cylinder 210
rectilinearly moves in the optical axis direction in unison with the cam
cylinder 209 and is then held at the WIDE position.

[0112]When the second movable cam cylinder 209 is extended in the optical
axis direction, the first group barrel 201 rectilinearly moves in the
optical axis direction by the engagement between the follower pins 201a
and the cam grooves 209c of the cam cylinder 209 so as to be relatively
separated from the second rectilinear guide cylinder 210, while being
rectilinearly guided by the rectilinear guide grooves 210a of the guide
cylinder 210.

[0113]When the lens barrel is in a retracted state, the extension piece
24a of the barrier drive ring 24 of the lens barrier mechanism provided
in the first group barrel 201 is in contact with the reception portion
210b of the second rectilinear guide cylinder 210. With movement of the
first group barrel 201 away from the guide cylinder 210, the extension
piece 24a is disengaged from the reception portion 210b, and an urging
force of the barrier spring 23 is released, whereby the barrier drive
ring 24 rotates to open the barrier blades 22. The first group barrel 201
further moves in the optical axis direction and is held at the WIDE
position (FIG. 2).

[0114]The position to which the first lens group 101 has been extended
relative to the CCD sensor 104 is decided as the sum of an amount of
forward movement (i.e., amount of movement toward the object side in the
optical direction) of the first rectilinear guide cylinder 208, an amount
of forward movement of the second movable cam cylinder 209, and an amount
of cam extension of the cam cylinder 209.

[0115]The position to which the second lens group 102 has been extended
relative to the CCD sensor 104 is decided as the sum of an amount of
forward movement of the first movable cam cylinder 107 and an amount of
cam extension of the cam cylinder 107.

[0116]When the zoom motor 212 is driven from the WIDE state corresponding
to the photographing region, the first group barrel 201 that holds the
first lens group 101 and the second group unit 202, 203 that holds the
second lens group 102 move along the optical axis as previously
described, and a TELE state shown in FIG. 3 is established.

[0117]The cam grooves 208d (FIG. 9) of the first rectilinear guide
cylinder 208 are formed on the inner peripheral surface of the regions Y
(FIG. 8) of the guide cylinder 208. Since the taper pins 208a are
disposed on the back side of the cam grooves 208d (i.e., on the outer
peripheral surface of the guide cylinder 208), the inclination of the
second movable cam cylinder 209 relative to the first movable cam
cylinder 207 is small.

[0118]Thus, the inclination of the first lens group 101 of the first group
barrel 201 that engages the second movable cam cylinder 209 relative to
the second lens group 102 of the second group unit 202, 203 that engages
the first movable cam cylinder 207 is also small.

[0119]In the photographing region from WIDE position to TELE position, the
AF motor 34 is driven according to the distance to object, whereby the
third group barrel 204 that holds the third lens group 103 is moved in
the optical axis direction for focusing.

[0120]In a case that the power supply is turned off, the zoom motor 212
rotates reversely and a storage operation is performed reversely to the
extension operation so that the lens barrel is moved to the retracted
position. During the movement to the retracted position, the follower
pins 209a of the second movable cam cylinder 209 are disengaged from the
cam grooves 208d and enter the cam grooves 208c so that a retracted state
is established.

[0121]Since the chamfers 208c1 are formed at the portions where the cam
grooves 208c are divided from the cam grooves 208d, the follower pins
209a can enter the cam grooves 208c without being caught, whereby a
smooth barrel retraction can be achieved.

[0122]Next, a description will be given of an example of driving control
for zoom operation of the lens barrel in this embodiment.

[0123]When power supply is turned on, a control unit (not shown)
determines whether the lens barrel is in a retracted position. The
control unit determines that the lens barrel is in a retracted position,
if the control unit does not detect a signal output from the photo
interrupter 36 when the light shield plate 210f provided on the second
rectilinear guide cylinder 210 retreats from a slit of the photo
interrupter 36 fixed to the CCD holder 206.

[0124]If the lens barrel is in a retracted position, the control unit
drives the zoom motor 212 to start a zoom operation. As a result, the
driving force of the zoom motor 212 is conveyed from a gear (not shown)
fixed to the motor shaft to the first movable cam cylinder 207 via the
gear train 213 and the gear 211, so that the cam cylinder 207 rotates.

[0125]Next, the control unit determines whether the first lens group 101
has been moved to a zoom reset position by determining whether the light
shield plate 210f of the second rectilinear guide cylinder 210 retreats
from the slit of the photo interrupter 36.

[0126]Specifically, in a case where the control unit detects a signal
output from the photo interrupter 36 when the light shield plate 210f
retreats from the slit of the photo interrupter 36, the control unit
detects that the first lens group 101 has been moved to the zoom reset
position.

[0127]If the signal indicating that the light shield plate 210f retreated
from the slit of the photo interrupter 36 has not been detected before
elapse of a predetermined time period, the control unit determines that
the first lens group 101 has not been moved to the zoom reset position,
and performs error processing.

[0128]The gear (not shown) fixed to the motor shaft of the zoom motor 212
is integrally formed with three blades that pass through the slits of the
two photo interrupters 38, 39.

[0129]The control unit converts a signal output when the passage of the
blades is detected by the two photo interrupters into pulses, and counts
the pulses to thereby detect the number of revolutions of the zoom motor
212.

[0130]Information representing the number of revolutions of the zoom motor
212 from a zoom reset position of the lens barrel to a zoom stop position
thereof such as WIDE position or TELE position is stored beforehand in a
memory.

[0131]When it is determined that the lens barrel has been driven to the
zoom reset position, a zoom count is reset and the lens barrel is moved
to the WIDE position. Subsequently, the third group barrel 204 is caused
to start moving to a focus reset position.

[0132]With the movement of the third group barrel 204, the light shield
plate 204b of the barrel 204 retreats from the slit of the focus photo
interrupter 37, and a change occurs in the output signal of the photo
interrupter 37.

[0133]If the output signal of the photo interrupter 37 does not change
before elapse of a predetermined time period, the control unit determines
that some trouble has occurred and performs an error process. If the
output signal of the photo interrupter 37 changes before elapse of the
predetermined time period, the control unit determines that the third
group barrel 204 has reached the focus reset position. Subsequently, the
third group barrel 204 reaches a WIDE standby position and a
photographing preparation is completed.

[0134]A stable optical performance can be attained even in the
construction including a large number of cylinders since only the first
group barrel 201 is interposed between the first lens group 101 and the
second rectilinear guide cylinder 210 during the series of zoom
operations and the light shield plate 210f for detection of the zoom
reset position is provided in the guide cylinder 210.

[0135]As described above, in the embodiment, the cam grooves 208d used in
the photographing region and the penetration cam grooves 208e used in the
retracted region are formed in the first rectilinear guide cylinder 208,
and the follower pins 209a engaging the cam grooves 208d and the drive
pins 209b engaging the penetration cam grooves 208e are formed in the
second movable cam cylinder 209.

[0136]Accordingly, the second movable cam cylinder 209 can be driven using
the penetration cam grooves 208e at places where the cam grooves 208c are
divided from the cam grooves 208d by the first rectilinear guide grooves
208f, whereby the lens barrel able to perform a smooth zoom operation can
be obtained.

[0137]Since the cam grooves 208c are divided from the cam grooves 208d at
a boundary between the retracted region and the photographing region, the
optical performance at the time of photographing is not adversely
affected, and therefore the highly reliable lens barrel can be obtained.

[0138]This invention is not limited in construction to the example
described in the embodiment, and various changes and modifications may be
made in terms of material, shape, size, form, number, installation
position, etc. without departing from the spirit and scope of the
invention.

[0139]For example, in the above embodiment, a case has been described
where the first group barrel 201 that holds the first lens group 101 and
the second group unit 202, 203 that holds the second lens group 102 are
moved in the optical axis direction by the cam engagement. Alternatively,
the first group barrel and the second group unit can be moved in the
optical axis direction by a helicoid mechanism.

[0140]In the above embodiment, the zoom lens barrel consisting of three
groups has been described. However, the present invention is applicable
to a zoom lens barrel consisting of two or four groups.

[0141]While the present invention has been described with reference to an
exemplary embodiment, it is to be understood that the invention is not
limited to the disclosed exemplary embodiment. The scope of the following
claims is to be accorded the broadest interpretation so as to encompass
all such modifications and equivalent structures and functions.

[0142]This application claims the benefit of Japanese Patent Application
No. 2009-188426, filed Aug. 17, 2009, which is hereby incorporated by
reference herein in its entirety.